The central theme of the proposed project is to develop a clear mechanistic understanding of the biosynthetic steps that lead to the beta-lactam antibiotics. The approach taken seeks to explore this problem in three ways. The first, in a refined stereochemical experiment, will examine the possible bioconversion of penicillin N to cephalosporin C. The remaining two problems deal with the biosynthesis of nocardicin A, an important new monocyclic beta-lactam-containing compound and clavlanic acid, a potent irreversible inhibitor of lactamase enzyme. Both of these compounds have been only recently discovered and very little is known about their biosynthesis.